1. Field of the Invention
The present invention relates to videoconferencing systems.
2. Description of the Related Art
Videoconferencing systems allow people at two or more different locations to participate in a conference so that the people at each location can see and hear the people at the other location(s). Videoconferencing systems typically perform digital compression of audio and video signals in real time. The hardware or software that performs compression is called a codec (coder/decoder). The resulting digital stream of bits representing the audio and video data are subdivided into packets, which are then transmitted through a network of some kind (usually ISDN or IP) to the other locations or endpoints participating in the videoconference.
Videoconferences can be performed using dedicated videoconferencing equipment, i.e., devices especially designed for videoconferencing. For example, a dedicated videoconferencing device may include input ports for receiving video signals from local video sources and audio signals from local microphones, network ports for receiving the remote audio/video streams from and sending the local audio/video stream to the remote endpoints, and output ports for displaying the video data on a display device and sending the audio data to an audio output device. The dedicated videoconferencing device may also include specialized software and hardware for compressing and decompressing audiovisual data, generating a composite image of the video streams from the various participants, etc. The dedicated videoconferencing device may also include an interface allowing users to interact with the videoconferencing equipment, e.g., to pan, tilt, and zoom cameras, select a video input source to send to the remote endpoints, control volume levels, control placement of video windows on the display device, etc.
Videoconferences can also be performed using non-dedicated equipment, e.g., a general purpose computer system. For example, a typical desktop PC can be configured to add-on hardware boards and/or software to enable the PC to participate in a videoconference.
Various standards have been established to enable the videoconferencing systems at each endpoint to communicate with each other. In particular, the International Telecommunications Union (ITU) has specified various videoconferencing standards. These standards include:
H.320—This is known as the standard for public switched telephone networks (PSTN) or videoconferencing over integrated services digital networks (ISDN) basic rate interface (BRI) or primary rate interface (PRI). H.320 is also used on dedicated networks such as TI and satellite-based networks.
H.323—This is known as the standard for video over Internet Protocol (IP). This same standard also applies to voice over IP (VoIP).
H.324—This is the standard for transmission over POTS (Plain Old Telephone Service), or audio telephony networks.
In recent years, IP-based videoconferencing has emerged as a communications interface and standard commonly utilized by videoconferencing equipment manufacturers. Due to the price point and proliferation of the Internet, and broadband in particular, there has been strong growth and use of H.323 IP-based videoconferencing. H.323 has the advantage that it is accessible to anyone with a high speed Internet connection, such as a DSL connection, cable modem connection, or other high speed connection.